Electronic Journal of Differential Equations, Vol. 2013 (2013), No. 03, pp. 1-8. Title: An approximation property of Gaussian functions Authors: Soon-Mo Jung (Hongik Univ., Jochiwon, South Korea) Hamdullah Sevli (Istanbul Commerce Univ., Turkey) Sebaheddin Sevgin (Yuzuncu Yil Univ., Van, Turkey) Abstract: Using the power series method, we solve the inhomogeneous linear first order differential equation $$ y'(x) + \lambda (x-\mu) y(x) = \sum_{m=0}^\infty a_m (x-\mu)^m, $$ and prove an approximation property of Gaussian functions. Submitted October 5, 2012. Published January 07, 2013. Math Subject Classifications: 34A30, 34A40, 41A30, 39B82, 34A25. Key Words: Linear first order differential equation; power series method; Gaussian function; approximation; Hyers-Ulam stability; local Hyers-Ulam stability.